1. Field of the Invention
The present invention relates to an electrical connector having a shield frame to shut off an electrical noise, and more particularly to an electrical connector to be used as a plug (hereinafter referred to as plug).
2. Discussion of The Related Art
As a plug so arranged as to shut off an electrical noise, there is known a plug having a shield frame made of metal. An electrical connector to be used as a socket (hereinafter referred to as socket) is selected as the counter member of the plug of the type above-mentioned. The socket has also a shield frame surrounding the peripheries of the contact pieces. When the plug is inserted into the socket, the shield frames of both the plug and the socket are electrically connected to each other to produce a shielding effect.
The plug and the socket may be connected to each other, for example, by inserting the plug into the socket mounted on a printed circuit board so that the socket contact pieces are contracted, under a predetermined contact pressure, with the plug contact pieces. The contact forces resulting from the pressure of the contact pieces generated at that time are so utilized as to prevent the plug from coming out from the socket.
However, the contact forces resulting from the pressure of the contact pieces mentioned above are not so great. Accordingly, if a signal cable connected to the plug is forcibly pulled on to apply a great pulling force to the plug, the plug is forcibly pulled out from the socket. This may result in an unexpected disconnection between the plug and the socket.
To prevent such an unexpected accident, it may be effective to dispose a locking mechanism which is adapted to automatically lock the plug and the socket when the plug is inserted into the socket, and which is adapted such that the locked state is not released unless a predetermined lock-releasing operation is carried out. As such electrical connectors, there are known a plug and a socket each provided on the outer surface thereof with a metallic locking mechanism, these locking mechanisms being adapted to be engaged with and disengaged from each other.
However, since these locking mechanisms are disposed on the outer surfaces of the plug and the socket, the locking mechanisms outwardly project from the plug and the socket. This presents the problem that the connectors are considerably increased in size and appear to be damaged.
Further, the engagement members and the members to be engaged of the locking mechanisms are made of metal. Accordingly, when a great force is applied to these engaged portions of the locking mechanisms in the locked state, the engagement members and the members to be engaged may be bent, deformed or bit by each other, causing the locking mechanisms not to be used any more.